1. Field of the Invention
The present invention relates to an optical subassembly and an optical transceiver, in particular, relates to a structure of the subassembly with an insulating sleeve cover for securing the sleeve.
2. Related Prior Art
The optical transceiver typically comprises a housing, into which a substrate for installing an electronic circuit and an optical subassembly for converting an optical signal into an electronic signal are installed. The housing also forms an optical receptacle for receiving an optical connector securing the optical fiber through which the optical signal is transmitted. The conventional optical subassembly is generally comprised of metal members from the viewpoints of mechanical toughness and the productivity, because the welding, especially the YAG laser welding, facilitates the assembling of the metal members.
However, such optical assembly comprised of wholly metal component exposes the metal parts at the optical receptacle, accordingly, the EMI (Electro-Magnetic Interference) noise comes in or radiates from the transceiver as the metal parts exposed to the outside operates as an antenna. Moreover, the optical connector typically made of resin is easy to be statically charged. When the charged optical connector inserts into the receptacle, the static charge accompanied with the connector may discharge through the metal sleeve exposed in the receptacle, which causes the spontaneous large current to break the electronic and optical devices installed in the transceiver.
An optical assembly with a sleeve cover made of resin has been developed instead of wholly metallic optical assembly. Japanese patent application published as 2001-066468 has disclosed such partially resin-made assembly. The optical assembly having such partially resin-made sleeve shows a superior performance for the EMI noise coming in the transceiver and for the switching noise of the large current for driving the laser diode (LD) from leaking from the transceiver. Moreover, the resin-made products inherently has a large insulation resistance, accordingly, the damages by the electrostatic discharge can be prevented.
On the other hand, such optical assembly partially comprising resin-made components has a subject that, because the welding can not apply to fix the components, the fixing strength does not increase and is not maintained, although the welding is a popular technique for fixing the whole metal assembly. To devise the structure of respective components of the assembly may increase and maintain the fixing strength between components. However, to devise the structure, or to make the structure of the assembly complex, results in the increase of the cost in both the components itself and the production thereof.